Neurotensin Stimulates Inositol Phospholipid Metabolism and Calcium Mobilization in Murine Neuroblastoma Clone N1E‐115

Murine neuroblastoma cells (clone N1E‐115) possess neurotensin receptors that mediate cyclic GMP synthesis. Because of the hypothesized relationship between phospholipid metabolism, intracellular Ca2+, and cyclic GMP synthesis, we determined with these cells the effects of neurotensin on 32P labeling of phospholipids, release of inositol phosphates, and intracellular Ca2+ (as determined with the use of Quin‐2, a fluorescent probe sensitive to free Ca2+ levels). Neurotensin stimulated incorporation of 32P into phospholipids, especially phosphatidylinositol and phosphatidate. Neurotensin also stimulated the release of [3H]‐inositol phosphates with an EC50 of about 1 nM. Mean basal Ca2+ concentration in these cells was 134 nM and this level was increased in a rapid and dose‐dependent manner by neurotensin, with an EC50 of 4 nM. Since the EC50 for neurotensin in stimulating cyclic GMP synthesis is 1.5 nM and the KD for binding of [3H]neurotensin at 0° is 11 nM, all these different effects appear to be shared proximal consequences of neurotensin receptor activation.